I'm gonna use some necro power and bump this up with an actual guide instead of a bad, text-based playthrough.
Southern Expansion Doctrine:
WW2 had just broke out and now, the Empire is ready to create a new world order in the Pacific.
The troops in Korea are to attack Beijing via Japanese held Manchuria. These troops are to defeat the Chinese vanguard, lay siege to Beijing and swiftly capture the city. Afterwards, send them into Northern China.
The Manchurian forces, led by Yamashita are to blitz into Siberia. You have 2 choices: (1) Send Yamashita towards Europe via the USSR and use troops to aid in the Alaskan Campaign. (2) Send Yamashita towards North America via Kamchakta and Alaska.
The troops in Taiwan are to attack Hong Kong. Let the fleet help capture Hong Kong them move them southward.
The forces on the main islands are to move against Shanghai. Use your destroyers in the western fleet to aid in its capture. The eastern fleet is to quickly capture Midway and defend against the American-Canadian attack. The northern fleet has to defeat the Soviet Pacific Fleet, capture their ports, hold the northernmost port, defend against the American Alaskan Fleet and capture the port at Alaska.
The Eastern Theatre
Here, your enemies are the USA and Canada.
Both of them are formidable foes, especially against our overstretched empire and they seek a decisive battle as well.
As mentioned, the eastern fleet will lead the attack on Midway. The troops will be light inf continuously raised in Tokyo. When Midway falls, prepare for the Allied counterattack.
The northern fleet has its own goals and will not contribute directly to the defence of the main islands. However, after they destroy the Alaskan fleet, assisted in the fall of Kamchakta and Alaska, and captured the surrounding ports, they should be sent to raid and harass the enemy along their west coast.
After sinking the enemy at sea, sail the Midway troops to Hawaii and capture it. I do recommend building up a force which will be sent to North America via neutral Mexico. If you want this second front to be more sucessful, quickly clear out Indonesia, the Philipines, New Guinea and Australia so that you can redeploy the troops there to your new front.
The Southern Gateway into Europe:
From Shanghai, attack via the Central plains towards the west.
From Hong Kong, attack into Southeast Asia via Vietnam.
With light inf spawned in Taipei and the western fleet, quickly conquer the Philippines and cut the region off from Australia.
When attacking India, the key to taking New Delhi is to geographically besiege the city, until you can directly conduct a siege of the city.
The rest is self-explanatory: Expand the empire, and keep on expanding.
The Northern Gateway into Europe:
The plan is simple. Attack with inf via the USSR into Europe. Make sure you use fast moving troops like motorised inf at the very least. Avoid tough cities (lvl 3 or above) if possible. Use the strategy which you employ on New Delhi to take these cities.
As for your troops in Northern China, send them westward and remember to take out Mongolia. Afterwards, it's just a clear attack into Europe via Central Asia and Stalingrad.
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And that's all for now.
raiyan, I hope this can answer your request for a guide to Japan 1939.